This disclosure relates to a charging circuit and a charging method thereof, and particularly to a multi-battery charging circuit and a charging method thereof which are able to improve charging efficiency of a plurality of batteries.
A process of charging of a battery is generally divided into a PC (pre-charging) phase, a CC (constant current) phase and a CV (constant voltage) phase.
The PC phase adopts a trickle mode to charge the battery, and a charging current in this phase is relatively small. When an amount of electric power of a battery is very low, using the trickle mode can avoid damage to internal structure of the battery due to an impact of a large current, so as to protect the battery, and a trickle charging may also prevent a problem of over-charging. However, time spent by the trickle charging is too long, and thus it is usually used in combination with other charging mode (e.g., a constant current charging, a constant voltage charging) in practice.
The CC phase adopts a constant current mode to charge the battery, a constant current is generally a maximum current allowable by a target battery, and an advantage of this charging mode is a fast charging velocity and a short charging time. However, since the battery itself generates a reverse potential to a charging current at the time of charging, a part of the charging current is converted into heat energy for counteracting the reverse potential, and thus larger the charging current is, more the heat energy converted is, and higher temperature at the time of charging is. Too high temperature would influence a service life of the battery, thus it is used in combination with other charging mode in practice.
The CV phase adopts a constant voltage mode to charge the battery, that is, charges the battery with a certain voltage, and the charging current would decrease gradually until the battery is fully charged according to a saturation level of a core of the battery in this phase. The constant voltage charging mode can prevent a battery voltage to be too high and cause over-charging, so as to achieve a purpose of protecting the battery.
In practice, the process of charging of the battery may be determined by a remaining amount of electric power of the battery, so as to include one or more of the above-described PC phase, CC phase and CV phase. For example, if the remaining amount of electric power of the battery is very much, the charging can be carried out by only executing the PC phase or the CV phase; and if the remaining amount of electric power of the battery is very few, the charging can be carried out by executing the above-described three phases in order sequentially.
However, with popularity of mobile apparatus, a requirement to endurance ability of the battery by the user increases, a single piece of battery is difficult to satisfy a requirement of a daily used mobile apparatus of the user. Adopting dual-battery or multi-battery to supply power is an effective way to extend the endurance ability of the battery. Taking power supply of the dual-battery as example, two kinds of charging schemes are generally adopted in practice: the first is adopting two charging circuits to use a charging mode of the above-described three phases to charge the two batteries respectively, and an advantage is a fast charging velocity and defects are a high cost and high temperature of the charging circuit; the second is adopting a single charging circuit to charge the two batteries in time-sharing.
Therefore, how to charge dual-battery or multi-battery more time saving and more efficiently in case of ensuring using a single charging circuit becomes a conventional technical problem to be solved.